. >> president obama has talked about red lines. >> yes. >> do you think bashar al assad has crossed a red line? >> not just for one time. many, many times he crossed the red line. >> what do you hope the united states does? >> i like them to help us to have no-fly zone for the whole country. >> nbc news chief foreign correspondent, richard engel joins me from turkey. richard, interesting interview. i've seen reporting on both sides that there wasn't proper custody control over some of the evidence as it was brought across the borders. that some samples were left in someone's car trunk for a number of days. are you persuaded about the evidence? or is it too early to tell what the allied intelligence services really believe is the case? >> i think it's very early to tell and i think it's probably impossible to assume that the rebels are going to treat materials and some sort of scientific or sanitary way. to give you an example, they believe that there was a chemical attack a few days ago in a town of sarakeb. at the same time of what they say was a chemical attack, still an unconfirm